Understanding the growth mode transition in InAs/GaAs(001) quantum dot formation

Scanning tunneling microscopy has been used to monitor the growth by molecular beam epitaxy of InAs quantum dots (QDs) on GaAs(001) at and near the critical coverage (theta(crit)). Direct evidence is obtained for the existence of small irregular 3D islands of height 6-12 Angstrom (2-4 ML) which contain similar to150 atoms or more. These features develop rapidly (within 0.05 ML of theta(crit)) into regular mature QDs with an average volume >1 X 10(4) atoms. Scaling analysis of the QD size distribution's suggests that strain may have a significant influence during QD nucleation and the initial stages of growth, but is unimportant during the later stages of QD development. (C) 2003 Elsevier Science B.V. All rights reserved.